myelomeningocele /mī′əlō′məning″gōsēl/ [Gk, myelos + menix, membrane, kele, hernia] , a developmental defect of the central nervous system in which a hernial sac containing a portion of the spinal cord, its meninges, and cerebrospinal fluid protrudes through a congenital cleft in the vertebral column. The condition is caused primarily by failure of the neural tube to close during embryonic development, although in some instances it may result from the reopening of the tube as a result of an abnormal increase in cerebrospinal fluid pressure. Also called meningomyelocele, myelocele, myelocystocele, myelocystomeningocele. Compare meningocele. See also neural tube defect, spina bifida cystica. ▪ OBSERVATIONS: The defect, which occurs in approximately 2 in every 1000 live births, is readily apparent and easily diagnosed at birth. Although the opening may be located at any point along the spinal column, the anomaly characteristically occurs in the lumbar, low thoracic, or sacral region and extends for three to six vertebral segments. The saclike structure may be covered with a thin layer of skin or with a fine membrane that can be easily ruptured, increasing the risk of meningeal infection. The severity of neurological dysfunction is directly related to the amount of neural tissue involved, which can be roughly estimated by the degree of the transillumination of the mass. Usually the condition is accompanied by varying degrees of paralysis of the lower extremities; by musculoskeletal defects such as clubfoot, flexion and joint deformities, or hip dysplasia; and by anal and bladder sphincter dysfunction, which can lead to serious genitourinary disorders. Hydrocephalus, frequently related to the Arnold-Chiari malformation, is the most common anomaly associated with myelomeningocele and occurs in approximately 90% of the cases in which the spinal lesion is located in the lumbosacral region. In most cases, hydrocephalus is apparent at birth, although it may appear shortly afterward. Supplementary diagnostic procedures include x-ray examination of the spine, skull, and chest to determine the extent of the vertebral defect and the presence of other malformations in other organ systems; a computed tomographic scan of the brain to establish the ventricular size and the presence of any structural congenital anomalies; and laboratory examinations, especially urine analysis, culture, blood urea nitrogen evaluation, and creatinine clearance determination. Amniocentesis is recommended for all pregnant women who have had a child with a neural tube defect. ▪ INTERVENTIONS: Immediate surgical repair is essential if the defect is leaking cerebrospinal fluid. However, surgical intervention may not be appropriate if neurological involvement is extreme, if the lesion is infected, or if associated problems, such as hydrocephalus, are severe. When surgical repair of the spinal defect is recommended, associated problems are managed by appropriate measures, including shunt procedures for correction of hydrocephalus; antibiotic therapy to reduce the incidence of meningitis, urinary tract infections, and pneumonia; casting, bracing, traction, and surgical techniques for correction of hip, knee, and foot deformities; and prevention and treatment of renal complications. Prognosis is determined by the severity of neurological involvement and the number of associated anomalies. With proper care and long-term maintenance most children can survive and do well. Early death is usually caused by central nervous system infection or by hydrocephalus, whereas mortality in later childhood is caused by urinary tract infection, renal failure, complications from shunt therapy, or pulmonary disease. ▪ PATIENT CARE CONSIDERATIONS: Immediate care centers on the prevention of local infection and trauma by carefully handling and positioning the infant, applying sterile moist dressings to the membranous sac, avoiding fecal contamination and breakdown of sensitive skin areas, and maintaining warmth, proper nutrition, and adequate hydration and electrolyte balance. Gentle range-of-motion exercises are carried out to prevent or minimize hip and lower extremity deformity. An important function of all members of the health care team is to involve the parents in the care of the infant as soon as possible and to teach them the essential procedures for adequate home care, including how to observe for signs of complications. The health care team also helps the parents in long-term management by planning activities appropriate to the developmental age and physical limitations of the child and by providing information for teaching all family members about the condition.
